Circuit arrangement including a voltage supply circuit and semiconductor switching element

ABSTRACT

A circuit arrangement comprising a first semiconductor switching element, which has a load path and a drive terminal. A voltage supply circuit, is provided including an inductance connected in series with the load path of the first semiconductor switching element, and a capacitive charge storage arrangement, which is connected in parallel with the inductance and which has a first and a second output terminal for providing a supply voltage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Utility patent application claims priority to German PatentApplication No. DE 10 2008 049 677.4-31, filed on Sep. 30, 2008, andincorporated herein by reference.

BACKGROUND

Semiconductor switching elements can be used as switches for switchingelectrical loads. Such semiconductor switching elements are, e.g., MOStransistors, such as MOSFET or IGBT. For driving the semiconductorswitching elements in the on state or in the off state drive circuitsare used, the drive circuits being connected to a drive terminal of thesemiconductor switching element and requiring a supply voltage forproviding a drive signal for the semiconductor switching element.

Drive circuits for semiconductor switching elements, which have to beable to provide a floating drive voltage for the semiconductor switchingelement, accordingly require a floating supply voltage. Such drivecircuits are, e.g., the drive circuits of n- or p-conducting MOSFETs, orof IGBTs, which are interconnected as high-side switches.

For providing a floating supply voltage for drive circuits ofsemiconductor switching elements, bootstrap circuits may be used, forexample. Further, transformers may be used that convert a supply voltagereferred to a reference potential to a desired supply voltage.

For these and other reasons there is a need for the present invention.

SUMMARY

One embodiment of the present disclosure relates to a circuitarrangement including a first semiconductor switching element having aload path and a drive terminal, and including a voltage supply circuit.The voltage supply circuit includes: an inductance connected in serieswith the load path of the first semiconductor switching element; acapacitive charge storage arrangement, which is connected in parallelwith the inductance and which has a first and a second output terminalfor providing a supply voltage.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of embodiments and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments andtogether with the description serve to explain principles ofembodiments. Other embodiments and many of the intended advantages ofembodiments will be readily appreciated as they become better understoodby reference to the following detailed description. The elements of thedrawings are not necessarily to scale relative to each other. Likereference numerals designate corresponding similar parts.

Examples are explained below with reference to drawings. The mainemphasis is on explaining the basic principle. Consequently, only thecircuit components and signals necessary for understanding this basicprinciple are illustrated in the drawings. In the drawings, unlessindicated otherwise, identical reference symbols designate identicalparts with the same meaning.

FIG. 1 illustrates one embodiment of a circuit arrangement including asemiconductor switching element and a voltage supply circuit.

FIG. 2 illustrates a circuit arrangement modified as compared with theembodiment in FIG. 1.

FIG. 3 illustrates one embodiment of a circuit arrangement including asemiconductor switching element, a voltage supply circuit and a drivecircuit for the semiconductor switching element, the drive circuit beingsupplied by the voltage supply circuit.

FIG. 4 illustrates one embodiment of a drive circuit.

FIG. 5 illustrates one embodiment of a voltage supply circuit thatgenerates a positive and a negative supply voltage.

FIG. 6 illustrates a further embodiment of a circuit arrangementincluding a semiconductor switching element and a voltage supplycircuit.

FIG. 7 illustrates one embodiment of a voltage supply circuit in which apositive and a negative supply voltage are generated in different ways.

FIG. 8 illustrates one embodiment of a voltage supply circuit thatgenerates supply voltages using inductances and bootstrap circuits.

FIG. 9 illustrates another embodiment of a circuit arrangement includinga semiconductor switching element and a voltage supply circuit.

FIG. 10 illustrates one embodiment of the use of a circuit arrangementincluding a semiconductor switching element and a voltage supply circuitin a half-bridge circuit.

FIG. 11 illustrates one embodiment of a circuit arrangement includingtwo voltage supply circuits coupled to one another.

FIG. 12 illustrates another embodiment of a circuit arrangementincluding a semiconductor switching element and a voltage supplycircuit.

FIG. 13 illustrates a variant of the circuit arrangement according toFIG. 12.

DETAILED DESCRIPTION

In the following Detailed Description, reference is made to theaccompanying drawings, which form a part hereof, and in which is shownby way of illustration specific embodiments in which the invention maybe practiced. In this regard, directional terminology, such as “top,”“bottom,” “front,” “back,” “leading,” “trailing,” etc., is used withreference to the orientation of the Figure(s) being described. Becausecomponents of embodiments can be positioned in a number of differentorientations, the directional terminology is used for purposes ofillustration and is in no way limiting. It is to be understood thatother embodiments may be utilized and structural or logical changes maybe made without departing from the scope of the present invention. Thefollowing detailed description, therefore, is not to be taken in alimiting sense, and the scope of the present invention is defined by theappended claims.

FIG. 1 illustrates by way of an electrical circuit diagram oneembodiment of a circuit arrangement including a semiconductor switchingelement 1, and a voltage supply circuit 2. The semiconductor switchingelement 1 has a drive terminal 11, first and second load path terminals12, 13, and a load path running between the load path terminals 12, 13.In the example illustrated, the semiconductor switching element 1 is anIGBT having a base terminal 11, which forms a drive terminal, acollector terminal 12, which forms a first load path terminal, and anemitter terminal 13, which forms a second load path terminal. It shouldbe pointed out that the use of an IGBT as semiconductor switchingelement 1 should be understood merely as an example. Instead of an IGBTit is possible, of course, to use any further semiconductor switchingelements, in one embodiment a MOSFET. In the case of a MOSFET, the driveterminal is formed by a gate terminal, and first and second load pathterminals are formed by drain and source terminals.

The semiconductor switching element 1 illustrated serves as a switch forswitching an electric current I1 flowing to an output terminal OUT. Anelectrical load Z may be connected to the output terminal OUT, the loadlikewise being illustrated in FIG. 1 (depicted by dashed lines) forexplanation purposes. Load Z may be any electrical load and may includein one embodiment a further semiconductor switching element that forms ahalf-bridge circuit with the semiconductor switching element 1illustrated in FIG. 1.

During operation of the circuit arrangement, the load path 12-13 of thesemiconductor switching element 1 is connected in series with the load Zbetween terminals for a positive supply potential V+ and a negativesupply potential V−. These supply potentials are also referred tohereinafter as load supply potentials. A voltage present between theterminals is referred to hereinafter as load supply voltage. Load Z maybe any passive or active electrical load.

The semiconductor switching element is, in one embodiment, a power IGBTor a power MOSFET having a voltage blocking capability from a few tensof volts up to a few kV depending on the specific form of realization. Afreewheeling element (not illustrated), such as e.g., a diode, may bepresent in parallel with the load path of the semiconductor switchingelement 1. In the case of a MOSFET, the freewheeling element can beformed by an integrated body diode.

The circuit arrangement has a voltage supply circuit 2 for providing asupply voltage V2. The supply voltage V2 can be used, in a manner thatwill be explained below, for example for the voltage supply of a drivecircuit (not illustrated in FIG. 1) of the semiconductor switch 1, butcan also be used for the voltage supply of any other circuit componentsof the circuit arrangement.

The voltage supply circuit 2 has an inductance 21 connected in serieswith the load path 12-13 of the semiconductor switching element 1 and,in the example illustrated, between the second load path terminal 13 andthe output terminal OUT. The inductance 21 is for example a parasiticinductance, such as e.g., a line inductance, a conductor trackinductance or a bonding wire inductance and is formed by lines,conductor tracks or bonding wires that are present between the outputterminal OUT and the second load path terminal 13—the emitter terminalin the case of an IGBT. However, the inductance can also be produceddeliberately in terms using circuit technology.

Connected in parallel with the inductance 21 is a capacitive storagearrangement 20, which, in the example illustrated, includes a seriescircuit including a rectifier element 22, such as e.g., a diode, and acapacitive storage element 23, such as e.g., a capacitor. In thisvoltage supply circuit 2, an electrical voltage V23 with respect to theelectrical potential of the second load path terminal 13 can be tappedoff across the capacitive storage element 23. This voltage V23 acrossthe capacitive storage element 23 can be used directly as supply voltageV2 at the output of the voltage supply circuit 2.

The voltage supply circuit 2 optionally has a voltage regulator 24 thatreceives the voltage V23 present across the capacitive storage element23, and that generates a regulated voltage V24 from the voltage V23present across the capacitive storage element 23, the regulated voltagebeing used as output voltage V2 of the voltage supply circuit 2. Thevoltage regulator 24 may be any voltage regulator, in one embodiment alinear regulator or a switching regulator, which is able to generate aregulated voltage V24 from the unregulated voltage present across thecapacitive storage element 23. The voltage regulator 24 may also berealized as a charge pump, or may include such a charge pump, and cantherefore be designed to generate a higher voltage V24 at its outputfrom the voltage V23 across the capacitive storage element.

During switching operations of the semiconductor switching element 1,electrical voltage is induced in the inductance 21. This inducedelectrical voltage is utilized in the voltage supply circuit 2 forcharging the capacitive storage element 23 of the charge storagearrangement, and thus for generating the supply voltage V2.

The voltage supply circuit 2 illustrated in FIG. 1 utilizes theelectrical voltage induced in the inductance 21 when the semiconductorswitching element 1 is turned off. For the purposes of the explanationit shall be assumed that the semiconductor switching element 1 isinitially driven in the on state by a drive circuit (not illustrated inmore specific detail). During this operating state, an electricalcurrent I1 flows through the load path 12, 13, and thus through theinductance 21, the electrical current being referred to hereinafter asload current. If the semiconductor switching element 1 is driven in theoff state, then the current I1 decreases. The associated temporal changedI1/dt in the load current I1 results in a voltage V21 induced in theinductance 21. For this voltage V21 applies:V21=L·dI1/dt  (1)where L denotes the inductance value of the inductance 21. In this case,the induced voltage V21 is the greater, the greater the inductance valueor the greater the temporal change in the current is.

In the embodiment illustrated, the temporal change in the load currentI1, and consequently the voltage V21 induced in the inductance 21, isnegative. In this case, the rectifier element 22 and the capacitivestorage element 23 of the charge storage arrangement 20 areinterconnected in such a way that the capacitive storage element 23 ischarged in the case of such a negative voltage V21, in which case apositive voltage V23 is present across the capacitive storage element 23relative to the electrical potential at the second load path terminal13. In the example illustrated, the rectifier element 22 is connectedfor this purpose in the forward direction between that terminal of theinductance 21 which is remote from the second load path terminal 13 andthe second load path terminal 13.

The voltage supply circuit 2 which is illustrated in FIG. 1, and which,for providing the supply voltage V2, can utilize parasitic inductancesthat are inevitably present, can be integrated together with thesemiconductor switching element 1 in a common semiconductor chip. Forproviding the supply voltage V2, no additional terminals at such anintegrated circuit including the semiconductor switching element 1 andthe voltage supply circuit 2 are necessary in this case.

As already explained, the supply voltage V2 generated by the voltagesupply circuit 2 can be used as supply voltage for a drive circuit (notillustrated in FIG. 1) of the semiconductor switching element 1. Inorder to make a supply voltage V2 available even before thesemiconductor switching element 1 has been driven in the on state forthe first time, or in order actually to enable the semiconductorswitching element 1 to be driven in the on state for the first time, astarting circuit 25, 26 is optionally provided. The starting circuit 25,26 is connected between a terminal for a supply potential, the terminalfor the positive load supply potential V+ in the example, and thecapacitive storage element 23 and has, in the example illustrated, anonreactive (ohmic) resistor 25 and optionally a further rectifierelement 26, for example a diode, connected in series with thenonreactive resistor 25. The starting circuit 25, 26 ensures that thecapacitive storage element 23 is already charged even before thesemiconductor switching element 1 is driven in the on state for thefirst time. The ohmic resistor 25 can have a very high resistance inorder to limit the power loss. The resistor may even have such a highresistance that the electrical energy supplied by using the startingcircuit 25, 26, in the case of clocked operation of the semiconductorswitching element 1, does not suffice to cover the energy supply of thedrive circuit (not illustrated). During the clocked operation, however,the energy supply is then ensured by using the electrical voltageinduced in the inductance 21.

A voltage limiting element (not illustrated) may optionally be connectedin parallel with the capacitive storage element of the charge storagearrangement, the voltage limiting element preventing the voltage V23from rising in an uncontrolled manner during the starting phase orduring operation. The voltage limiting element used can be, by way ofexample, a Zener diode in addition to the rectifier element 22. As analternative, such voltage limiting can also be achieved by the rectifierelement 22 being realized as a Zener diode or as a series circuitincluding a plurality of Zener diodes. The voltage across the rectifierelement 23 is limited to approximately 10 V to 20 V, for example.

Such voltage limiting can be used in all the voltage supply circuitsadditionally explained below, even if that is not explicitly pointed outbelow. The same applies to the starting circuit.

The optionally present rectifier element 26 of the starting circuit 25,26 prevents the capacitive storage element 23 from being discharged inthe direction of the terminal for the positive load supply potential V+if the semiconductor switching element 1 is turned on. If thesemiconductor switching element 1 is turned on, then the second loadpath terminal 13 is approximately at the positive supply potential V+.In this case, the electrical potential at that terminal of thecapacitive storage element 23 which is remote from the second load pathterminal 13 lies above the electrical potential at the second load pathterminal 13 by the value of the voltage V23, such that the capacitivestorage element 23 would be discharged via the starting circuit if therectifier element were not present. The rectifier element 26 can beomitted for example when the resistor 25 has a very high resistance andwhen the semiconductor switching element is driven in clocked fashion,that is to say is switched on and off in clocked fashion. In this case,although the omission of the rectifier element 26 leads to an increasein the power loss, during the switched-on duration of the semiconductorswitching element the capacitive storage element is not discharged tosuch an extent that the generation of the supply voltage is interrupted.

FIG. 2 illustrates a voltage supply circuit 2 with a starting circuitthat is modified as compared with the voltage supply circuit inaccordance with the embodiment of FIG. 1. In the case of the circuitarrangement illustrated in FIG. 2, the load supply voltage is generatedby a rectifier 3 having input terminals 35, 36 for applying an inputvoltage Vn, e.g., a power supply voltage, and output terminals 37, 38for providing the load supply voltage. In the example illustrated, oneof the output terminals is connected to the negative supply potential V,and the positive load supply potential V+ is available at the other ofthe output terminals. A smoothing capacitor 39 is optionally present forsmoothing the voltage present at the output terminals 37, 38. In theexample illustrated, the rectifier 3 is realized as a bridge rectifierhaving four rectifier elements, such as diodes. If a three-phase inputvoltage is present, then the rectifier 3 may be extended by a furtherrectifier branch having two rectifier elements in a sufficiently knownmanner.

In the case of this circuit arrangement, a starting circuit 27, 28 has afurther rectifier element 28 and a capacitor 27, which are connected inseries with one another between one of the inputs of the rectifier 3 andthe capacitive storage element 23 of the voltage supply circuit 2. Inthe case of this circuit, the capacitor 27 and the capacitive storageelement 23 of the voltage supply circuit 2 form a capacitive voltagedivider, which together with the further rectifier element 28 functionin the manner of a peak rectifier. In this case, the capacitive storageelement 23 is charged to a voltage which is related to the maximum valueof the voltage present at the input. A relationship of the voltage atthe capacitive storage element 23 and the input voltage is given by thedivider ratio of the capacitive voltage divider.

FIG. 3 illustrates one embodiment of a circuit arrangement having adrive circuit 4 for driving the semiconductor switching element 1. Thedrive circuit 4 includes an output terminal 44 connected to the driveterminal 11 of the semiconductor switching element, a drive signal S1being available at the output terminal 44. The drive circuit 4additionally includes voltage supply terminals 41, 42 that receive thesupply voltage V2 provided by the voltage supply circuit 2. The supplyvoltage, in the manner explained, is either directly the voltage V23present across the capacitive storage element 23 or the voltage V24present at the output of the voltage regulator 24.

The drive circuit 4 additionally includes a drive input 43 for receivinga switching signal Sin, in accordance with which the drive circuit 4generates the drive signal S1. In a manner not illustrated in morespecific detail, the switching signal Sin is generated for example by acentral control circuit, such as e.g., a microcontroller. This centralcontrol circuit is, for example, galvanically isolated (decoupled) fromthe drive circuit 4. In this case, the transmission of the switchingsignal Sin from the central control circuit is effected via a potentialbarrier, such as e.g., an inductive transformer or an optocoupler, or alevel shifter.

The switching signal Sin is a two-valued signal, for example, which mayassume a switch-on level or a switch-off level. The drive circuit 4 isconfigured to convert the switching signal Sin into a drive signal S1suitable for driving the semiconductor switching element 1. In theexample illustrated, the drive signal S1 is a voltage relative to thesecond load path terminal 13 of the semiconductor switching element 1.The IGBT illustrated in FIG. 3 is turned on if the voltage is greaterthan a threshold voltage specific to the component, and is turned off ifthe voltage is less than the threshold voltage. The maximum value thatcan be assumed by the drive voltage S1 present at the output of thedrive circuit 4 corresponds to the supply voltage V2 the drive circuit 4receives from the voltage supply circuit 2. In the case of the circuitarrangement illustrated in FIG. 3, in which the voltage supply circuit 2generates a supply voltage V2 referred to the second load path terminal13 of the semiconductor switching element 1, the smallest value that canbe assumed by the drive voltage S1 is zero. The drive circuit 4explained may also be used for driving an n-channel MOSFET in a mannercorresponding to that for driving an IGBT.

It should additionally be pointed out that the voltage supply circuitsexplained above and those additionally explained below are, of course,not restricted to being used in circuit arrangements with n-channelcomponents, rather the voltage supply circuits may also be used in acorresponding manner in circuit arrangements with p-channel components.

FIG. 4 illustrates the circuit diagram of one embodiment of a drivecircuit 4. The drive circuit 4 illustrated includes an output stage withtwo complementary transistors 45, 46 that have their load pathsconnected in series with one another between the supply terminals 41, 42of the drive circuit 4. In the embodiment illustrated, the transistors45, 46 are MOS transistors. However, these transistors may also berealized as bipolar transistors in a corresponding manner.

A circuit node common to the load paths of the transistors 45, 46 formsthe output 44 of the drive circuit 4. The two transistors 45, 46 aredriven by a common control circuit 47 depending on the switching signalSin. Depending on the signal level of a signal S47 present at the outputof the control circuit 47 only one of the two transistors 45, 46 in isturned on at a point in time. If the upper transistor 45 of the twotransistors 45, 46—the upper transistor being a p-MOSFET in theembodiment illustrated—is turned on, then the drive voltage S1corresponds to the difference between the electrical potential at thefirst supply terminal 41 and the electrical potential at the second loadpath terminal 13. In the case of the circuit arrangement illustrated inFIG. 3, the difference corresponds to the supply voltage (V2 in FIG. 3).If the lower transistor 46 of the two transistors 45, 46—the lowertransistor being an n-MOSFET in the example illustrated, —is turned on,then the drive voltage S1 corresponds to the difference between theelectrical potential at the second supply terminal 42 and the electricalpotential at the second load path terminal 13—which is zero in the caseof the example in accordance with FIG. 3. In the case of this drivecircuit 4, the upper transistor 45 is driven in the on state when theswitching signal Sin assumes a switch-on level, and the lower transistor46 is driven in the on state when the switching signal Sin assumes aswitch-off level. The control circuit 47 converts the switching signalSin into the signal S47 suitable for driving the transistors 45, 46. Thecontrol circuit 47 may furthermore additionally realize furtherprotection functions that are known in principle, such as e.g., anovertemperature protection. If such an overtemperature protection ispresent, then the drive circuit 4 turns off the semiconductor switchingelement 1 during operation when a temperature in the region of thesemiconductor switching element 1 exceeds a predetermined temperaturethreshold value.

In the case of the voltage supply circuit illustrated in FIG. 3, astarting circuit may likewise be present, of course, in accordance withthe explanations concerning FIGS. 1 and 2. The starting circuit is notillustrated in FIG. 3, however, for reasons of clarity.

FIG. 5 illustrates a further embodiment of a voltage supply circuit 2.This voltage supply circuit 2 differs from the voltage supply circuitsexplained previously in that it also provides, in addition to a positivesupply potential referred to the second load path terminal 13, anegative supply potential referred to the second load path terminal 13.In addition to the already explained first series circuit including thefirst rectifier element 22 and the first capacitive storage element 23,the charge storage arrangement 20 of this voltage supply circuit 2 has asecond series circuit including a second rectifier element 52, such ase.g., a diode, and a second capacitive storage element 53, such as e.g.,a capacitor. This second series circuit is likewise connected inparallel with the inductance 21, wherein the second rectifier element 52is oppositely polarized with respect to the first rectifier element 22.In the case of this voltage supply circuit 2, electrical charge isstored in the second capacitive storage element 53 when the voltage V21present across the inductance 21 is a positive voltage. In the exampleillustrated, positive voltages are induced in the inductance 21 when thesemiconductor switching element 1 is switched on, that is to say when aload current I1 flowing through the semiconductor switching element 1rises. In the embodiment illustrated, a voltage V53 present across thesecond capacitive storage element 53 is an electrical voltage that isnegative relative to the second load path terminal 13. The sum of thevoltages V23, V53 provided by the two capacitive storage elements 23, 53may be used directly as supply voltage V2 for the drive circuit 4. Inthis case, the first supply terminal 41 of the drive circuit 4 isconnected to the first capacitive storage element 23 and the secondsupply terminal 42 is connected to the second capacitive storage element53.

Optionally the electrical voltages V23, V53 present at the capacitivestorage elements 23, 53 are converted to regulated voltages V24, V54 byvoltage regulators 24, 54. In this case, a first voltage regulator 54generates a regulated voltage V24 from the voltage V23 across the firstcapacitive storage element 23, and the second voltage regulator 54generates a second regulated voltage V54 from the voltage V53 presentacross the second capacitive storage element 53. In this case, the sumof these two regulated voltages V24, V54 corresponds to the supplyvoltage V2 provided by the voltage supply circuit 2.

Feeding a negative supply potential in addition to a positive supplypotential relative to the potential of the second load path terminal 13to the drive circuit 4 has the advantage that the drive signal can alsoassume negative values for driving the semiconductor switching element 1in the off state in addition to positive values for driving thesemiconductor switching element 1 in the on state. A more rapid turn-offof the semiconductor switching element 1 can be achieved using negativedrive voltages S1 as compared with using a drive voltage of zero in thecase of the circuit arrangement according to FIG. 3.

In the voltage supply circuit 2 according to FIG. 5, a starting circuitmay be provided in accordance with the explanations that have been madewith reference to FIGS. 1 and 2, the starting circuit being coupled tothe first capacitive storage element 23. The starting circuit is notillustrated in FIG. 5, however, for reasons of clarity. A furtherstarting circuit may be provided in a corresponding manner, whichprovides for a first charging of the second capacitive storage element53 even before the semiconductor switching element 1 has been driven inthe on state for the first time. The further starting circuit includesfor example a series circuit including a resistance element 55 and arectifying element 56, this series circuit being connected between theterminal for the positive supply potential V+ and the second capacitivestorage element 53. Instead of this starting circuit including theresistance element 55 and the rectifying element 56, a starting circuitwhich couples the second capacitive storage element 53 to a rectifiercircuit via a rectifying element and a capacitor may also be provided inaccordance with the explanations that have been made with reference FIG.2.

It was assumed for the explanations above that the semiconductorswitching element 1 is interconnected as a high-side switch, that is tosay that the load path is connected between the terminal for thepositive supply potential and the load Z. However, the voltage supplycircuit explained does also function in a corresponding manner for asemiconductor switching element used as a low-side-switch, as isillustrated in FIG. 6. In this case, the load path 12, 13 of thesemiconductor switching element 1 is connected between the load Z andthe negative supply potential V−. The voltages V21 induced in theinductance 21 during the switching of the semiconductor switchingelement correspond to the voltages that are induced in the inductance 21if the semiconductor switching element is connected up as a high-sideswitch. The voltage supply circuit 2 illustrated in FIG. 6 for thepurposes of explanation corresponds to the voltage supply circuit 2explained above with reference to FIG. 5. It should be pointed out inthis context that any other of the voltage supply circuits explainedpreviously can also be used instead of this voltage supply circuit 2.The illustration of starting circuits has been omitted in the case ofthe voltage supply circuit 2 illustrated in FIG. 6. It goes withoutsaying that such starting circuits may be provided.

Generation of the supply voltage V2 using an inductance connected inseries with the load path 12-13 of the semiconductor switching element 1may be combined with further measures for generating the supply voltageV2 from the electric circuit of the load. FIG. 7 illustrates oneembodiment of a voltage supply circuit 2 which combines two differentmeasures for generating the supply voltage. The voltage V53 that isnegative relative to the reference point—i.e., the second load pathterminal 13—is generated using the inductance 21, as already explained.For this purpose, the second capacitive storage element 53 is connectedto the inductance via the second rectifier element 52.

In this circuit the positive voltage V23 is generated using a capacitivedivider. A first terminal of the first capacitive storage element 23 isconnected to the first load path terminal of the semiconductor switchingelement 1 via a series circuit including a coupling capacitance 61 and arectifier element 62, such as a diode, and the second terminal of thefirst capacitive storage element 23 is connected to the second load pathterminal of the semiconductor switching element 1. A voltage whichcorresponds to the load path voltage V1 of the semiconductor switchingelement is present across the series circuit including the firstcapacitive storage element 23, the coupling capacitance 61 and therectifier element 62.

The voltage V1 rises each time when the semiconductor switching elementis turned off. The first capacitive storage element 23 is then chargedeach time to a voltage which is related to the load path voltage. Arelationship between these two voltages is given by the divider ratio ofa capacitive voltage divider formed by the capacitive storage element 23and the coupling capacitance 61. If the semiconductor switching elementis subsequently driven in the on state, whereby the load path voltage V1decreases, then the rectifier element 62 prevents the capacitive chargestorage element from being discharged.

In a manner not illustrated in more specific detail, it is also possibleto utilize a bootstrap principle for generating the negative supplyvoltage and the inductance 21 for generating the positive supplyvoltage.

FIG. 8 illustrates one embodiment of a circuit arrangement in which thepositive supply voltage V23 and the negative supply voltage V53 aregenerated both using the inductance and using the capacitive dividerprinciple. For this purpose, the voltage supply circuit 2 includes thecircuit components already explained with reference to FIGS. 5 and 6and, in addition, the divider circuit explained with reference to FIG.7, the divider circuit also being supplemented by a further rectifierelement, which is connected between that terminal of the secondcapacitive storage element 53 which is removed from the reference nodeand the coupling capacitance, and which enables the second capacitivestorage element 53 to be charged in the case of a rising load pathvoltage of the semiconductor switching element 1.

The reference point for the supply voltage generated by the voltagesupply circuit 2 is dependent on the position of the inductance 21within the load path electric circuit. In this case, the load pathelectric circuit is the electric circuit containing the load path 12-13of the semiconductor switching element 1. In the case of the circuitarrangements explained previously, the inductance 21 is connecteddirectly to the second load path terminal 13 of the semiconductorswitching element 1. In this case, the supply voltage V2, or the partialsupply voltages V23, V53 and V24, V54, are referred to the second loadpath terminal 13 of the semiconductor switching element 1. Through asuitable choice of the position of the inductance 21 within the loadpath electric circuit, it is also possible, of course, to generatesupply potentials which are referred to different electrical potentialsthan the electrical potential of the second load path terminal 13.

FIG. 9 illustrates one embodiment of a circuit arrangement in which thevoltage supply circuit 2 generates supply potentials which are referredto the positive load supply potential V+. In this case, the inductance21 is connected between the terminal for the positive load supplypotential and the load path 12-13 of the semiconductor switching element1. The load supply potential can be generated—as has already beenexplained in connection with FIG. 2—for example using a rectifier and acapacitor 39 connected downstream of the rectifier. Only the capacitor39 is illustrated in FIG. 7, for reasons of clarity. The inductance 21is for example a line inductance of a conductor track or of some otherelectrically conductive connection between the terminal at which theload supply potential V+ is available and the load path 12-13 of thesemiconductor switching element 1 and/or a bonding wire inductance. Thevoltage supply circuit 2 is connected to the inductance 21 in the sameway as explained previously. The voltage supply circuit 2 illustrated inFIG. 9 corresponds to the voltage supply circuit already explained withreference to FIG. 5 and is designed to generate a partial supply voltageV23 or V24 which is positive relative to the positive load supplypotential V+ and a partial supply potential V24 or V54 which is negativerelative to the load supply potential V+, the sum of which correspondsto the supply voltage V2. It goes without saying that any other of thevoltage supply circuits explained previously can also be used instead ofthis voltage supply circuit 2. Thus, by way of example, the seriescircuit including the second rectifier element 52 and the secondcapacitive storage element 53 and the optional voltage regulator 54 canbe dispensed with if only a supply potential V23 or V54 which ispositive relative to the positive load supply potential V+ is intendedto be generated, which forms the supply voltage V2. In a correspondingmanner, in the case of the voltage supply circuit 2 illustrated in FIG.9—as well as in the case of the voltage supply circuits 2 alreadyexplained with reference to FIGS. 5 and 6—there is the possibility ofdispensing with the series circuit including the first rectifyingelement 22 and the first capacitive storage element 23 if only a supplypotential that is negative relative to the reference potential isintended to be generated, which forms the supply voltage. The referencepotential is the electrical potential of the second load path 13 in thecase of the examples in accordance with FIGS. 5 and 6 and the loadsupply potential V+ in the case of the example in accordance with FIG.7.

FIG. 10 illustrates one embodiment of a circuit arrangement having twosemiconductor switching elements 1 ₁, 1 ₂, each having a drive terminal11 ₁, 11 ₂ and also first and second load path terminals 12 ₁, 12 ₂, 13₁, 13 ₂. These two semiconductor switching elements 1 ₁, 1 ₂ which arerealized as IGBTs in the example illustrated, are interconnected as ahalf-bridge by their load paths 12 ₁-13 ₁, 12 ₂-13 ₂ being connected inseries with one another between terminals for a positive load supplypotential V+ and a negative load supply potential V−. An output OUT ofthe half-bridge is formed by a node common to the load paths of the twosemiconductor switching elements 1 ₁, 1 ₂. A load Z′ (illustrated bydashed lines in FIG. 8) can be connected to the output OUT.

Drive circuits 4 ₁, 4 ₂ are present for driving the two semiconductorswitching elements, supply voltages V2 ₁, V2 ₂ respectively being fed tothe drive circuits by voltage supply circuits 2 ₁, 2 ₂. The voltagesupply circuits 2 ₁, 2 ₂ can be in each case any one of the voltagesupply circuits explained above. In order to provide the supply voltageV2 ₁ for the drive circuit 4 ₁ of the high-side switching element 1 ₁,the voltage supply 2 ₁ utilizes two inductances: a first inductance 21A,which is connected between the second load path terminal 13 ₁ of thefirst semiconductor switching element 1 ₁ and the output OUT of thehalf-bridge; and a second inductance 21B, which is connected between theoutput OUT of the half-bridge and the first load path terminal 12 ₂ ofthe second semiconductor switching element 1 ₂. In this case, use ismade of the fact that voltages V21A, V21B across these two inductances21A, 21B each have the same polarity if the two semiconductor switchingelements 1 ₁, 1 ₂ are respectively driven complementarily to oneanother, that is to say are respectively driven in such a way that onlyone of the two semiconductor switching elements is driven in the onstate at the same point in time. This is briefly explained below: forthis purpose it shall be assumed that at a given point in time the firstsemiconductor switching element 1 ₁ is driven in the on state and thesecond semiconductor switching element 1 ₂ is driven in the off state.In this case, a load current I₁ flows via the first semiconductorswitching element 1 ₁ and the output terminal OUT to the load, while asecond load current I₂ through the second semiconductor switchingelement 1 ₂ is zero. If, at a later point in time, the firstsemiconductor switching element 1 ₁ is driven in the off state and thesecond semiconductor switching element 1 ₂ remains turned off, then avoltage V21A not equal to zero is induced only in the first inductance21A, which voltage is utilized by the voltage supply circuit 2 ₁ forproviding the supply voltage V2 ₁. If the load Z is an inductive loadand if the second semiconductor switching element 1 ₂ is driven in theon state when the first semiconductor switching element 1 ₁ is turnedoff, such that the second semiconductor switching element 1 ₂ acceptsthe previously flowing load current, then a load current starts to flowthrough the second semiconductor switching element 1 ₂ counter to thecurrent direction illustrated in FIG. 10. A voltage V21B is therebyinduced in the second inductance 21B, the voltage having the samepolarity as a voltage V21A induced in the first inductance 21A when thefirst load current I1 ₁ decreases.

The half-bridge illustrated in FIG. 10 is for example part of anH-bridge circuit which also include, in addition to the half-bridgeillustrated, a further half-bridge, which can be realized in a mannercorresponding to the half-bridge illustrated in FIG. 10. The half-bridge10 illustrated in FIG. 10 can additionally be part of an inverter fordriving a three-phase motor. In this case, in addition to thehalf-bridge illustrated, two further half-bridges are also present,which can be realized in a corresponding manner.

The voltage supply circuit 2 ₂ that supplies the drive circuit 4 ₂ ofthe low-side semiconductor switch utilizes, for providing the supplyvoltage V2 ₂, the inductance 21 ₂ present between the second load pathterminal 13 ₂ and the terminal for negative supply potential V−.

FIG. 11 illustrates examples of the voltage supply circuits 2 ₁, 2 ₂illustrated in FIG. 10 for the generation of two supply voltages V2 ₁,V2 ₂ in detail. These two voltage supply circuits 2 ₁, 2 ₂ arerespectively realized in accordance with the voltage supply circuitsexplained with reference to FIGS. 5 and 6 and respectively generate apositive and a negative supply voltage. Starting circuits optionallypresent are not illustrated in FIG. 11. In the case of the circuitarrangement in accordance with FIG. 11, a rectifier element is connectedbetween the first capacitive charge storage elements 23 ₁, 23 ₂ of thevoltage supply circuits 2 ₁, 2 ₂. This rectifier element 64 enablescharge equalization—bootstrap principle—between the two charge storageelements 23 ₁, 23 ₂, whereby the reliability of the circuit arrangementincreases overall to the effect that a sufficient drive voltage can begenerated for both semiconductor switching elements 1 ₁, 1 ₂. In theexample illustrated, the rectifier element 64 is polarized in such a waythat the first charge storage element 23 ₁ of the first voltage supplycircuit 2 ₁ can be charged by the first charge storage element 23 ₂ ofthe second voltage supply circuit 2 ₂.

The charge equalization between the two first capacitive charge storagearrangements 23 ₁, 23 ₂ as explained above is independent of thespecific realization of the voltage supply circuits 2 ₁, 2 ₂. Instead ofthe voltage supply circuits illustrated in FIG. 11, any other voltagesupply circuits from among those explained above could also be used, inone embodiment there also being the possibility of realizing the twovoltage supply circuits 2 ₁, 2 ₂ differently.

In the example illustrated in FIG. 11, the second voltage supply circuit2 ₂ utilizes two inductances: an inductance at the second load pathterminal 13 ₂ of the second semiconductor switching element 1 ₂, whichinductance is formed by bonding wires, for example; and an inductance 21₄ of a lead or voltage supply line to the half-bridge circuit 1 ₁, 1 ₂.It goes without saying that the second voltage supply circuit 2 ₂ couldalso be realized in such a way that it utilizes only one of theseinductances.

In this context it should again be mentioned that, in the case of allthe voltage supply circuits explained above, the inductances do not haveto be separate components, rather parasitic inductances are utilized asinductances, such as e.g., leakage inductances, conductor trackinductances, bonding wire inductances, or inductances that are formed bythe geometrical construction of the circuit which includes the at leastone semiconductor switching element. In the case of conductor trackinductances, the inductance is “distributed” over the entire length ofthe conductor track, such that the inductance which is effective forvoltage generation can be set by the choice of the connection points ofthe charge storage arrangement at the conductor track. It goes withoutsaying that it is possible for these inductances that are present anywayto be increased in a targeted manner, for example by the geometry of theline routing being chosen in a suitable manner.

FIG. 12 illustrates one embodiment of a voltage supply circuit that isable to generate, from inductances adjacent to the first load pathterminal 12, a supply voltage V2 referred to the potential at the secondload path terminal 13. The voltage supply circuit 2 illustratedgenerates two voltages: a first voltage V23, which is positive relativeto the potential at the second load path terminal 13; and a secondvoltage V53, which is negative relative to the potential at the secondload path terminal 13. Regulated voltages can be generated from thesevoltages in the manner explained. It goes without saying that it is alsopossible for only one of these voltages V23, V53 to be generated; thecircuit components required for generating the respective other voltagecan then be omitted.

Starting circuits are not illustrated in FIG. 12, but may of course beprovided.

The voltage supply circuit 2 illustrated includes the first and secondstorage capacitances 23, 53 already explained. Unlike in the case of thevoltage supply circuits explained previously, however, these storagecapacitances in the example illustrated, via the first and secondrectifier elements, are not connected directly to the inductanceutilized for voltage generation, but rather to a capacitive buffer store70. The capacitive buffer store includes two capacitive buffer storeelements 72, 74, such as capacitors, for example, which are eachconnected in series with a rectifier element 71, 73, such as a diode,for example. The two rectifier elements are polarized differently andare respectively connected between the buffer store element 72, 74 andthat terminal of the inductance which is remote from the first load pathterminal 12, or the terminal for the upper supply potential V+.

The series circuits each including a buffer store element 72, 74 and arectifier element 71, 73 are connected in parallel with one another andconnected to the inductance. This inductance is composed of two partialinductances in the example illustrated: a first partial inductance 21 ₁adjacent to the first load path terminal 12, the first partialinductance being formed by bonding wires, for example; and a secondpartial inductance 21 ₃, which is a lead inductance, for example. Itgoes without saying that it is also possible to utilize only one ofthese inductances for voltage generation.

The buffer store elements 72, 74 are charged during different switchingoperations of the semiconductor switching element: the first bufferstore element 72 is charged when the semiconductor switching element 1is switched on, if a positive voltage V21 in induced in the inductance21 ₁, 21 ₃; and the second buffer store element 73 is charged when thesemiconductor switching element 1 is switched off, if a negative voltageV21 is induced in the inductance 21 ₁, 21 ₃. The first buffer storeelement 72 is connected via a switching element 75—and the firstrectifier element 22—to the first capacitive charge storage element 23,to be precise at a terminal remote from the first load path terminal 12.The switching element 75 is driven in the on state, for example, if thesemiconductor switching element is turned on, and, when thesemiconductor switching element 1 is driven in the on state, enables thefirst capacitive storage element 23 to be recharged. When thesemiconductor switching element 1 is driven in the on state, the secondcapacitive storage element 53 is also recharged (bootstrap principle),to be precise directly via its rectifier element 52, which is connectedto the second buffer store element 74, to be precise at a terminalremote from the first load path terminal 12.

FIG. 13 illustrates one embodiment of the voltage supply circuit 2explained above in which the switching element 75 is realized as anormally off transistor, as a JFET in the example. This JFET is drivenby the drive circuit 4 of the semiconductor switching element 1. Thedriving of the JFET 75 can be effected synchronously with thesemiconductor switching element, but can also be effected in such a waythat the JFET is driven in the on state only temporarily duringswitched-on durations of the semiconductor switching element. In thiscase, the switch-on phase of the JFET can lie temporally arbitrarilywithin a switch-on phase of the semiconductor switching element.

The circuit arrangements explained above can be used, for example, inintelligent power modules (IPM, integrated power modules).

Finally, it should be pointed out that circuit features that have beenexplained only in connection with one example can be combined withcircuit features from other examples even if this has not beenexplicitly explained above. Thus, in one embodiment, features that aredescribed in any of the claims below can be combined with features ofany other claims.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisinvention be limited only by the claims and the equivalents thereof.

What is claimed is:
 1. A circuit arrangement comprising: a firstsemiconductor switching element having a load path and a drive terminal,the load path running between a first load path terminal and a secondload path terminal; and a voltage supply circuit, for providing a supplyvoltage the voltage supply circuit comprising: a first side of aninductance connected in series with the load path of the firstsemiconductor switching element via the second load path terminal; and acapacitive charge storage arrangement that includes a circuit with arectifier element and a capacitive storage element, a cathode of therectifier element directly coupled to a first side of the capacitivestorage element via a first node, a second side of the capacitivestorage element directly coupled to the second load path terminal, andan anode of the rectifier element directly coupled to a second side ofthe inductance via a second node, wherein a voltage across thecapacitive storage element is the supply voltage.
 2. The circuitarrangement of claim 1, wherein the inductance comprises at least one ofthe following inductances: a leakage inductance, a conductor trackinductance, a bonding wire inductance, an inductance governed by ageometrical construction of the circuit arrangement.
 3. The circuitarrangement as claimed in claim 1, furthermore comprising: a drivecircuit having voltage supply terminals, connected to the outputterminals of the voltage supply circuit, and having a drive outputconnected to the drive terminal of the semiconductor switching element.4. The circuit arrangement as claimed in claim 1, furthermore comprisinga second semiconductor switching element having a load path and a driveterminal, wherein the inductance is arranged between the load paths ofthe first and second semiconductor switching elements.
 5. A circuitarrangement comprising: a first semiconductor arrangement having a loadpath running between a first load path terminal and a second load pathterminal; and a voltage supply circuit comprising: a first side of aninductance coupled in series with the load path of the firstsemiconductor switching element via the second load path terminal; and acapacitive charge storage arrangement including a first circuit having arectifier element and a capacitive storage element, a cathode of therectifier element directly coupled to a first side of the capacitivestorage element via a first node, a second side of the capacitivestorage element directly coupled to the second load path terminal, andan anode of the rectifier element directly coupled to a second side ofthe inductance via a second node.
 6. The circuit arrangement of claim 5,further comprising: a starting circuit coupled to the capacitive storageelement.
 7. The circuit arrangement of claim 6, wherein the startingcircuit includes a nonreactive resistor.
 8. The circuit arrangement ofclaim 7, the starting circuit including a further rectifier elementcoupled in series with the nonreactive resistor.
 9. The circuitarrangement of claim 6, the voltage supply circuit further comprising: avoltage regulator configured to generate a regulated voltage from avoltage across the capacitive storage element.
 10. The circuitarrangement of claim 5, the voltage supply circuit further comprising: avoltage regulator configured to generate a regulated voltage from avoltage across the capacitive storage element.